Anatomy and Histology of the Small and Large Intestine, Lecture notes of Neuroanatomy

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Topic 9: The

Digestive System

9.3: Small and Large Intestine

http://health-advisors.org/human-digestive-system-for-kids/

1. Describe anatomy and histology of small

intestine

2. Describe anatomy and histology of large

intestine

Learning Outcomes

The Small Intestine: Histology

Fig 24.19 (a,b) ; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson.

 Four layers of the intestinal wall:

The Small Intestine: Histology

1. Mucosa layer

contains:

 Cells & gland

 mucosa-associated

lymphoid tissue

(MALT)

2. Submucosa layer

contains:

 Duodenal glands

secrete alkaline

mucus

Fig 24.19 (c) ; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson. ? ? ? ?

Histology of SI (Ileum)

Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson.

Surface Area for

Digestion & Absorption

 Surface area increases by having:

1. Circular folds

 Plicae circulares

 Permanent ridges of mucosa and submucosa

 Cause chyme to spiral

2. Villi

 Fingerlike projections of mucosa

 Contains arteriole, venule, blood capillary,

and lacteal

3. Microvilli

 Projects of apical membrane of absorptive

cells

 Brush border with brush border enzyme

? ? ?

Accessory Digestive Organs associated with SI  Accessory digestive organs

1. Liver
2. Gallbladder
3. Pancreas

 = the largest gland of the body

 has four lobes

 Composed of liver lobules

made of hepatocytes (liver

cells)

Liver

Function of the Gall Bladder

 Function:

 to store and to concentrate bile produced by the liver

(absorb water & electrolytes; concentrate up to 10X)

 When bile is needed in the small intestine:

 Cholecystokinin (CCK)  induce contraction of smooth muscle

Pancreas

a | Gross anatomy of the pancreas. b | The exocrine pancreas. c | A single acinus. d | A pancreatic islet embedded in exocrine tissue. (^) http://www.nature.com/nrc/journal/v2/n12/fig_tab/nrc949_F1.html

 Lies posterior to greater

curvature of stomach.

 Composed of:

 Acini (99%)

 Secrete pancreatic juice –

mixture of fluid &

digestive enzymes

 Islets of Langerhans (1%)

 Secrete hormones

glucagon, insulin,

somatostatin &

pancreatic polypeptide

The Large Intestine

Fig 24.18 (a) ; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson. ? ? ? ? ?

The Large Intestine: Anatomy

Fig 24.18 (a, b) ; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson.

 Four regions of the large intestine:

 Colon is divided

into ascending,

transverse,

descending

and sigmoid

colon

The Large Intestine: Histology

Fig 24.19 (a,b) ; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson.

 Four layers of the intestinal wall:

 Mucosa:

 mostly

absorptive and

goblet cells

 No circular folds

 No villi but have

microvilli

 Muscularis

 Longitudinal

muscle modified

to form teniae

coli

 Forms haustra –

pouches

 WHY?

The Large Intestine: Histology

; Principles of Anatomy and Physiology, 13th Edition. by Gerard J. Tortora , Bryan H. Derrickson. ? ?